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Innovative Thinking

Learning about Terminal Blocks

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At Premier Automation, we use terminal blocks in almost all our builds. A terminal block is an electrical junction point that allows two or more wires to be connected at the same electrical potential. These also provide added functionality as they allow for easier rework of electrical circuits, convenient test points, and are finger safe to protect a user. Just like wire comes in many different types and sizes, terminal blocks do as well based on application.

            The most common types of terminal blocks are screw-in, spring-loaded, push-in, fused, and ground type terminal blocks. Some less common terminal types such as plug, isolating blade terminals, and diode terminals. Differences between types of terminal block are either their connection technology that holds the wire, or in the electrical device that comes installed within the terminal block.


For the different termination types, a screw-in terminal block uses a screw to force two contact plates to close around a wire for a secure connection. They are also one of the most common terminal block. Spring-loaded style blocks have a clamp where tension is held with a spring. The spring is compressed using a tool, the wire is inserted, and then the spring is released which holds pressure on the wire. Push-in types are very similar to the spring-loaded blocks, except that they use a button to compress the clamp instead of a spring. Multi-tiered terminal blocks that provide more connection points are available for all different connection types.


Some terminal blocks come with different devices built in which saves space in the panel or makes installing those devices easier. The fused terminal block is the most common of these. This type of block comes with a removable housing that holds a small fuse inside. Wires that are connected to either side are connected directly through the fuse. Isolating blade terminals come with levers that disconnect the internal connection bus so one side of the terminal doesn’t connect to the other. Terminal blocks with diodes installed can also be purchased so you don’t need to solder two wires onto either end of a single diode.


Ground terminal blocks are special in that their internal connection bus is tied directly to the clamps that hold them to din rail. Because the din rail is connected directly to the grounded subpanel, any connections to a ground terminal block also connect to the subpanel ground. This allows the user to conveniently add many grounds across the panel.


Terminal blocks come in many different sizes to accommodate different wire gauges. During the selection process, it is important to check what wire range a terminal block accepts. There are also different accessories you can purchase such as jumpers that connect multiple terminal blocks, covers that make open style terminal blocks finger safe, and end anchors that lock in place to prevent items from moving on the din rail.


            Because of the convenience and versatility of terminal blocks, Premier Automation uses terminal blocks in almost all our builds to make it easier for us to wire our panels and cabinets. Our customers find that using terminal blocks keeps wiring easy to troubleshoot and makes post-installation changes and updates much simpler.



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